    [Patent document 1] JP-H6-88733 A
There is known a navigation apparatus in a subject vehicle to learn a new road not registered in map data based on a travel locus of the subject vehicle. Patent document 1 recites a navigation apparatus to generate route data based on travel locus generated when traveling a region other than roads registered in the map data, thus learning a new road which is not registered in the map data. According to the navigation apparatus in Patent document 1, for instance, if a certain road, which is not registered in the map data, is newly built, the certain road can be learned by a subject vehicle traveling the certain road. Therefore, without need of updating the map data from an outside, it becomes possible to execute a process of a route search covering such a newly built road.
In this regard, however, according to the above-mentioned navigation apparatus in Patent document 1, for example, even if the subject vehicle enters a parking lot etc. from a road registered in the map data, and then moves inside of the parking lot, there is a possibility of learning as a new road the route corresponding to the travel locus inside of the parking lot. In addition, even if a travel locus of the subject vehicle is mistakenly detected as a travel locus in a region other than roads registered in the map data because of measurement errors, there is a possibility of learning the mistakenly detected travel locus as a new road. Thus, the navigation apparatus in Patent document 1 has a possibility to learn as a new road a road which does not exist really.